Patent GB-595146-A (GB)
Title: Improvements in or relating to time-controlled electric switches
IPC: H05G1/40
Filed: 1945-02-02
Abstract: 595,146. Time switches; press-button retractive switches. RITTER CO., Inc. Feb. 2, 1945, No. 2720. Convention date, Feb. 3, 1944. [Class 38(v)] [Also in Group XX] A time switch for X-ray apparatus comprises the combination of an electrical switch means and variable timing means operated by adjustable indicating means located adjacent, and adapted for movement relative to, a fixed indicating means, and a further indicating means adapted to be set with relation to the first adjustable means to control, by means of the setting action tensioning a spiral spring in a time switch of known type, the duration of exposure in accordance with the setting. The exposure triggering button 40, which may be retained in the operative position by the turned end of an L-shaped slot, is attached to one end of a springy strip which is attached at the other end to the top of a framework 16, 17, supported on a front plate 57 by pillars 16a, the strip engaging, at a position just above the union with the button 40, a plunger 28 slidable in guide slots in the lower portion of the framework to free a spindle 23 carried thereby from the action of springs 25, 26, allowing an anti-clockwise tensioned spring 18 to drive a shaft 21 by means of a gear train and a fan governor 24, carried on spindle 23. The movement of plunger 28 also causes simultaneously the finger 35 of lever 30, pivoted on the plunger at 29 and spring-biassed in a clockwise direction to engage the tip 36 of lever 37, pivoted at 45 on a post 46 carried by frame member 16, thus closing spring-mounted contacts 50, 51 and completing the circuit between terminals 48, 55 mounted on an insulating strip 49. A dog 33 fixed on shaft 21 engages, as it returns to its initial position, the inclined face 32 of lever 30, tripping finger 35 out of engagement with lever 37 thus opening the circuit; and releases the button 40 from its locked engagement by striking a pin 44 on the strip 39. The exposure setting device consists of (1) a stationary dial plate 60 secured to a plate 57 closing the open end of the timing mechanism housing 11 and carrying a sleeve 58 which loosely surrounds the shaft 21; (2) a dial 63 preferably provided with two scales, one for size of jaw and the other for different teeth locations, mounted on the sleeve 58 and provided with an arcuate slot 62 through which the age scale 61, Fig. 6, on dial 60 is visible, and an extension 65 which protrudes from a slot 66 in the casing and allows the dial 63 to be rotated in a fixed ring 64 cut away to allow passage of the extension; and (3) a transparent notched dial 69, carrying an arrow 71, fixed on the outer end of the spindle 21 as by means of a hub 70 keyed thereto. A further fixed scale 73 marked in seconds of exposure may be carried by a ring 74 screwed on to the ring 64. By rotating the dial 63 the appropriate indication on the jaw size scale 67 is registered with the appropriate agegroup on scale 61. The dial 69 is then rotated until the arrow 71 points to the teeth location which is to be radiographed, this setting of dial 69 rotating the shaft 21 anti-clockwise thus tensioning the spring 8 which determines the length of exposure.